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Subject: Re: Help understanding null move

Author: Bruce Moreland

Date: 10:10:06 01/28/00

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On January 28, 2000 at 07:39:17, Mark Taylor wrote:

>In null move, (as I understand it- please correct me if I'm wrong), a player
>misses a move (i.e. lets the opponent play 2 moves in succession), and if no
>significant change in the eval occurs then further searching from that node is
>abandoned (on the basis that if you can up a move without suffering then your
>position must be solid)?

If you give a guy a free punch at you, and he can't cause any significant
damage, perhaps this is a good predictor of the outcome of the fight, and you
can avoid it.

>My question is this - being forced to make a move in Chess can be disastrous in
>certain positions (esp. in the endgame), and in this type of position misleading
>results would be obtained.

This is correct.  That is why it is not done in the endgame.

>It seems to me that a better approach would be to make a single move (any move)
>rather than no move at all - the resulting tree would be the same size and
>therefore the overheads should not be that much greater.

You are trying to figure out if they have any threats even if you put up no
defense.  Making a move might either create a defense or wreck your position, so
it would inject a degree of uncertainty into the whole thing.

In practice null move will make any program much better tactically, at almost no
cost.

bruce




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